Solar-friendly building design

Wouldn’t it be great if a new building could be designed and constructed with a future solar installation in mind? Just think of the time, effort and money that could be saved if your home or business could have solar installed with relative ease.

We frequently find ourselves lamenting various elements of a home or business that reduce the capacity of the system or that require us to use additional equipment or labor for the system to be installed. Given current trends, we often tell clients, “If you are building or designing a new structure today, it will almost certainly have solar installed on it during its expected lifespan.”

But what does it mean for a house to be solar ready? Here are the key elements that architects and builders should consider in new construction if optimization for solar power is a priority:

Roof orientation: The most important quality for a solar-ready home or business is its orientation to the sun, also known as the “azimuth” (or compass angle). South-facing roofs are the best for collecting maximum sunlight year-round but, thanks to ever-improving solar panels, we can work with west, southwest, east, or southeast-facing roofs as well. When siting a new building on a piece of property, keep in mind the overall building orientation as it relates to the sun. The closer to a due south azimuth you can achieve for at least one major roof face, the better your solar production – and return on investment – will be.

Roof pitch: The angle – or “pitch” – of a roof is an important consideration for solar. Exact pitch depends on the latitude of the location where the system will be installed. Sarasota is at 27 degrees north latitude, so a 27-degree array is optimal for our area. However, anything within 10 degrees of that will lose less than 2% annual production so we generally aim for an angle between 15 and 20 degrees, typically a 4/12 or 5/12 pitch. This increases your summertime production somewhat (at the expense of that overall annual loss). Steeper pitches can be difficult to install on since it’s difficult for our crew members to maintain their footing on angles exceeding 20 degrees.

A flat roof will be just fine, too. With the reductions in the cost of solar over the past five years, solar will work well on a flat roof (i.e. a zero degree tilt angle – interestingly, the azimuth angle, in this case, does not matter since the array is flat), with a loss of only about 9.5% annual production, as compared to a 27 degree due south tilt angle.

When the solar panels comprised a much larger portion of the overall cost of a solar array, it made sense to tilt up the solar panels on a flat roof, as the additional cost of engineering and materials was lower than the cost of additional panels. Today, with panels costing so much less, it’s usually less expensive to just add more panels to a flat array to make up for the loss of production, rather than tilting the panels. Additionally, inter-row shading (where one row of panels shades the row behind it) increases as tilt angles increase; tilting also reduces the number of panels that can be installed.

In these cases, we often recommend a tilt angle of five or, at most, 10 degrees, which does improve dirt shedding and minimizes inter-row shading, while also minimizing additional wind uplift on the panels. However, if space is at a premium, or if there is a desire to maximize the amount of annual solar production, a flat array is totally viable and allows for maximum packing of panels on the rooftop.

Rooftop obstructions: The solar array is going to be fighting for space with other construction features such as plumbing vents, attic vents, skylights, chimneys, and other roof-mounted equipment. Having clear contiguous areas of roof space, with few obstructions, means larger solar arrays can be installed; the resulting arrays are easier to install and more aesthetically pleasing. Sometimes, simply grouping vent stacks, or lining them up on one side or in a line (instead of placing them randomly across a roof surface), can open up enough space to make solar much easier to install.

Dormers: To make the installation of the solar array as easy as possible, it is important to have the largest possible contiguous roof space. Like vent stacks and other obstacles, dormers, “bump-outs” and other roof plane alterations make solar difficult, so try to minimize those on the south-facing roof plane.

Shade: Builders should be sure to plan the south-facing roof space for a shade-free area of the building site, if possible. It is important to know which way any trees, nearby buildings, or other structures will cast their shadows; ideally, sunlight should be unobstructed between 9 a.m. and 3 p.m., which is the peak production time for the solar array each day.

Roof material: By far the best type of roof for solar, due to its durability and energy efficiency, is the standing seam metal roof. A complete solar array can be installed on a standing seam metal roof without a single penetration of that roof system. Second best is standard roof shingles; there are excellent roof flashing systems for shingle roofs – we have installed thousands of these and never had a single leak. 5V metal roofs (which can be identified by their exposed fasteners) are next – there are very good products for attaching to 5V roofs.

Tile roofs are by far the most difficult and expensive roof system to install solar on. Tile roof flashings are much more costly and the labor to install them is significantly higher than standing seam, shingle or 5V roofs. If you are planning a tile roof, please contact us very early in your planning since we can recommend methods to mitigate the complexity and cost of installing solar on a tile roof. With the proper planning, solar can be done easily and cost-effectively – even on a tile roof – and the results are very attractive.

Roof load: If a home is built to code, the additional load of solar panels (~3 pounds per square foot) will not be an issue. The only time that solar can be an issue in terms of roof loading is when there is a need to tilt the panels up relative to the roof surface (i.e., so they are no longer parallel to the roof surface). In this case, additional reinforcement of the roof structure may be needed to accommodate the additional wind uplift from the solar panels during a storm. Understanding this ahead of time will dramatically lower the cost of installing a tilt-up array, if one is necessary.

Wiring: Most residential solar installations require a run of 1″ metallic conduit from the attic area under the proposed array location back to the main electrical panel or utility meter area. It is much easier to install the conduit while the walls are open – trust us on that one!

There are numerous other factors, such as planning for solar in the breaker panel, allocation of space near the main electrical panel for PV inverters and other equipment, aesthetics related to the solar array, and more. But there is no element of planning for solar that is too difficult or that renders a new home to be prohibitively expensive. With advance planning and the proper expertise, a new building owner can enjoy 25 years or more of energy at a fraction of what they might be paying today, thanks to their solar power system.

Please do not hesitate to give us a call at (941) 359-3700 for more information or guidance on this topic.